Desulfurization process



1958 H. A. HOLCOMB ET AL 2,865,850

DESULFURIZATION PROCESS Filed Sept. 6, 1955 3 Sheets-Sheet 2 1. w T R D 0 R N 0 LB 0 0 ED 0 Y 0 5 w ML 6 6 Mm E 6"!- A0 1 R L 5 A M 5m W E C E D A 00 [c E F a R LZ L E T U/ W H A W7 w F M N mszo. m an 6A5 E 65.! 0 M s a r 0 E A RHM 4 06 0 r r u 0 M o S H Cw 2H H 6, w F mm 0 0 m m H 0 M M s. M M N. H 2 NN Mu. n Mr L N L 0 R 5 NW 6 0M M L M L w. m a

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w a m 0 MOL H 5 llV FEED HATER/AL AT REACTOR INLET F I G. 3.

h m m T 0 N c E/ V 0 mH A y. r n e H By Morris R. Mar/0 w.

A T TORNE' Y.

H. A. HOLCOMB ETAL 2,865,850 I DESULFURIZATION PROCESS 3 Sheets-Sheet 3 IN V EN TORS A T TORNE Y.

Henry A. Holcomb, By Morris A. Morrow.

mm M L mm M 5 Y L RH um m M 6. N a. a irm YT T Du AL 0 OX S a 0 MM 5 M 5 .1 M w m7. 0 L ME F 5 4 M00 L w 5 o M 6-! L! JLP a 5 MUS w u u r T 6 L M u 0 A w a Rw 0 E OUG n JE v: mu F HTW s m 0 HE M Z s 0 EM. M 0m EMF NH U L P 1. A 0 H 5 HN IN NNE. 00 W ,V b\4 0 0 0 0 m a 6 4 2 4 3 2 I Dec. 23, 1958 Filed Sept. 6, 1955 FIG. 4.

HYDROGEN PART/AL PRESSURE, 251-4.-

- DESULFURIZATIUN PROCESS Henry AtHolcomb and Morris R.'MOI'I'OW, Baytown, Tex., assignors, by mesne assignments, to Esso Research and. Engineering Company,.llizabeth, N. 3., a corporation of Delaware Application September 6, 1955; Serial No. 532,706

6 Claims. ((31. 208-212) This invention relates to a process for desulfurizing petroleum hydrocarbon products boiling in the naphtha range. More particularly, this invention relates to a process for desulfurizing a petroleum hydrocarbon fraction boiling in the naphtha range by contact with a desulfurization catalyst in the presence of hydrogen and added hydrogen sulfide under selected reaction conditions whereby a desulfurized product having improved Saybolt color characteristics and reduced mercaptans content and gum content is obtained.

The process of the present invention may be briefly described as contacting a petroleum hydrocarbon feed stock boiling within the range of about 275 to 430 F. with a desulfurization catalyst in the presence of about 250 to 2,000 cubic feet of hydrogen per barrel of feed stock and about 0.1 to 10 mol percent ofadded'hydrogen sulfide (H 8), based on the total amount of feed material, under reaction conditions including a temperature Within the range of about 500 to about 750 F. (T space velocity in the range of about 1 to about 16 volumes of feed per volume of catalyst per hour (v./v./hr.), a reactor pressure Within the range of about 50 to about 300 pounds per square inch gauge and a hydrogen partial pressure within the range of about 50 to about 150pounds per square inch absolute, said reaction conditions .at least substantially satisfying the equation:

--Product mercaptan number (M)=1' /.8+ 0.43 (v./v./hr.)

+1.3 (percent H S)0.03 (T wherein M has a value within the range of about 0.1 to about 10, and preferably about 0.1 to about 5.

In accordance with the present invention it has been discovered that when gum-containing petroleum hydrocarbon naphthas are brought into contact with a desulfurization catalyst in the presence of added hydrogen sulfide an improved degree of desulfurization can be obtained, such improved desulfurization being accompanied by an improvement in the Saybolt color characteristics of the product. It has been further discovered that there is a tendency towards the formation of products containing undesirable amounts of organic inercaptans and that this tendency can be largely inhibited by properly controlling reaction conditions. Moreover, it has been discovered that gum content can be materially reduced by conducting the reaction under conditions wherein a hydrogen partial pressure within the range of about 50 to about 150 pounds per square inch absolute is employed. The tendency towards the formation of mercaptans may be inhibited by interrelating the amount of added hydrogen sulfide with space velocity and reaction temperature in order to at least substantially satisfy the mercaptan control equation Product mercaptan number (M)=17.8+O.43 (v./v:/hr.) +1.3 (percent H S)0.03 (T wherein M has a value within the range of about 0.1 toabout 10.

2,865,850 Patented Dec. 23, 1958 obtained inaccordance with the Potentiometric Mercaptan Number Testldescribed by R. W. Tamele and L. B.

Ryland in an article entitled Potentiometric Determination of Mercaptans (Ind.'Eng.1Chem., Anal. Ed., 8, 16, 1936) andwidely used throughout the industry.

Gum content, as referredto throughout the specification vis'the General Motors gum content determined in accordance with the memes. described in A. S. T. M. Test No.

.D-381-54T employing a bath-temperature of about 174 "to about 182 C.

The feed stock-tobe employed in accordance with the present invention may be derived from a petroleum crude oil or from a thermally or catalytically treated portion thereof. Thus, for example, thefeed stock may bea 'virgin naphtha, a naphtha fraction derived from the thermal or catalytic cracking of a petroleum crude oil or a fraction thereof, a naphtha derived from the polymerization of-lower boiling unsaturated hydrocarbons such as ethylene,- propylene, butylenes, butene, etc. Mixtures of two or more such materials may also be used'if desired. i Representative naphth-a'fractions of this nature may be derived from West Texas crude petroleums, Panhandle crude petroleums, Gulf Coast crude petroleums and the'like and fromgasoline boiling range hydrocarbons derived -ther'efrom during catalytic or thermal conversion and processing operations. For

- commercial reasons, it'is preferable to employ naphthas boiling'within the range of about 275 to 430 F.

The-naphta' feed stock should be vcontacted with a suitable desulfurization catalyst, numerous examples of which are known to those skilled inthe art. Examples of suitable catalysts; are the oxides and sulfidesof metals such as V, Cr, Mn, Fe, Co, .Ni, Mo, W, 'etc., oxides of platinum and palladium, etc. Specific. examples of such catalysts are cobalt molybdate, nickel-tungsten. sulfide, cobalt sulfide, molybdenum oxide, nickel sulfide, tin sulfide, etc. 'The catalysts are preferably. employed .in particulate form supported on a suitable carriersuch as alumina; magnesia,. silica, zinc oxide,. kieselguhr, etc. which may or may not, asdesired, contain silica. The catalyst may be employed in thev form .of a fixed bed catalyst,.in the form of a fluidized bed, or in any other suitable manner well known. to those skilled in the art.

In order to obtain des'ulfurization, the feed stock is brought into contactwith the desulfurization catalyst in the presence of hydrogen and added hydrogen sulfide. Theamount of hydrogen to be employed should, generally speaking, be Within therange of about 250 to 2,000 cubic/feet of hydrogen per barrelof feed stock. In accordance with a preferred embodiment of .the. invention, about 500 to about 1,000 cubic feet of hydrogen per barrel of feed stock is employed.

Hydrogen for. the process may be provided by charging a hydrogen-containing gas. to the catalyst along'with the mixture of hydrogen and inertgas, a mixture of hydrogen and light hydrocarbons e. g., a hydrogen-containing oifgas from a catalytic reforming. process),.etc. Hydrogen which. is not consumed during the .desulfurization reaction may, if desired,be recycled.

The amount of hydrogen sulfide to be added should preferably be within the range of about 0.1 to about 10 mol percent of hydrogen sulfide, based on the total amount of feed material and preferably in the range of about 0.1 to about 5 mol percent. The term feed material includes the feed stock, the hydrogen, the added hydrogen sulfide and such other inert gaseous materials as may be charged to the reactor.

The hydrogen sulfide to be added may be hydrogen sulfide normally present in the gaseous hydrogen-containing feed gas or may be hydrogen sulfide which is separately added from an extraneous source.

The reaction conditions to be employed include a temperature Within the range of about 500 to about 750 F., a space velocity within the range of about 1 to about 16 volumes of feed per volume of catalyst per hour, and a reactor pressure within the range of about 50 to about 300 pounds per square inch gauge. In accordance with a preferred form of the invention, a temperature of about550 to about 700 F., a space Velocity of about 2 to about 6 v./v./hr. and a pressure of about 150 to about 250 p. s. i. g. are employed. The reactor pressure and hydrogen charge rate should be correlated to provide a hydrogen partial pressure in the reactor within the range of about 50 to about 150 pounds per square inch absolute.

The process of the present invention may also be con sidered in conjunction with the accompanying drawings wherein:

Fig. 1 is a schematic diagram illustrating one preferred manner in which the process of the present invention may be accomplished; and,

Figs. 2 to 5 are graphs illustrating the effect of reaction conditions on the percent desulfurization, Saybolt color and gum content.

Turning now to Fig. 1, the numeral 10 designates a reaction zone containing a suitable desulfurization catalyst. A suitable preheated naphtha feed stock derived from any suitable source (not shown) is charged to the desulfurization zone 10 through aline 12 in admixture with a gaseous material containing hydrogen and hydrogen sulfide which is supplied through a line 14. Within the desulfurization zone 10 the feed materials are brought into contact with the desulfurization catalyst in order to obtain desulfurization of the naphtha feed stock and the reaction products are discharged from the desulfurization zone 10 through a line 16. The line 16 passes to a suitable cooling means 18 wherein the reaction products are cooled to an extent sufficient to liquefy the products boiling in about the naphtha boiling range and the thuscooled mixture is fed by way of a line 20 to a suitable separator 22 wherein phase separation occurs between the liquefied and gaseous or vaporous components of the reaction products. The liquefied material is discharged from the separator 22 through a line 24 and the gaseous and/or vaporous material, comprising hydrogen, hydrogen sulfide and normally gaseous hydrocarbons is discharged overhead through a line 26 controlled by a valve 34.

The liquefied material discharged through the line 24 comprises the desulfurized product and may be recovered as such. However, it has been discovered that during the desulfurization reaction higher boiling components are formed which tend to increase the final boiling point of the product. When the desulfurized product is to be utilized in the preparation of commercial grades of gasoline, and when the final boiling point of the feed stock is up to a limiting final boiling point for gasoline products, as is normally the case, it is desirable that the above-mentioned higher boiling components be removed from the liquefied product. In this situation, the liquid material in the line 24 is charged to a suitable fractionation zone,such as a distillation column 28 wherein the liquid material is distilled to provide an overhead product boiling in the gasoline range and delivered through a line 30 and to provide a bottoms fraction delivered through the line 32 comprising the undesirable higher boiling components.

The gaseous material discharged from the separator 22 through the overhead line 26 may be discarded from the system if it is desired to supply all of the hydrogen and hydrogen sulfide required for desulfurization from extraneous sources or, if desired, all or part of the gaseous materials may be recycled to the desulfurization zone 10. Even when the gaseous material is to be recycled, however, it will generally be necessary to supply extraneous hydrogen in that the desulfurization reaction normally consumes at least a portion of the hydrogen charged to the desulfurization Zone 10.

If the gaseous material is to be recycled, care should be taken to compensate for the hydrogen sulfide contained therein which was formed in the desulfurization reactions. If the gaseous material is substantially freed from hydrogen sulfide or contains up to the maximum amount of hydrogen sulfide to be used, the gaseous material may be directly recycled. In this instance, any addi tion hydrogen sulfide that is required may be supplied from an extraneous source.

When the gaseous material contains an excessive amount of hydrogen sulfide, it may be treated to remove all or an appropriate amount of the hydro-gen sulfide or, as an alternative, part of the gaseous material may be admixed with a hydrogen-containing gas from an extraneous source which does not contain excessive hydrogen sulfide in an amount sufficient to provide a mixture having the desired hydrogen sulfide and hydrogen content.

Thus, with respect to Fig. 1, all of the gaseous material may be discarded from the separator 22 through the discharge line 26 controlled by the valve 34 and the hydrogen and hydrogen sulfide requirements may be met by charging hydrogen to the feed line 14 from an extraneous source (not shown) through a hydrogen feed line 44 controlled by a valve 46 and by charging an appropriate amount of hydrogen sulfide from an extraneous source (not shown) through the hydrogen sulfide charge line 40 controlled by a valve 42.

As another example, and when the gaseous material discharged from the separator 22 does not contain an excessive amount of hydrogen sulfide, a valve 36 in a recycle line 38 may be opened and the valve 34 in the discharge line 26 may be regulated so that all or a portion of the gaseous material may be recycled to the feed line 14 through the recycle line 38. As indicated, an additional amount of hydrogen may be simultaneously charged to the feed line 14 through the hydrogen charge line 44. In addition, and if necessary, hydrogen sulfide may be charged to the feed line 14 through the hydrogen sulfide charge line 49.

As another alternative, and when the gaseous material contains an excessive amount of hydrogen sulfide, all or a part of such gaseous material may be recycled through the line 38 in the indicated manner and the recycled material may be diluted with an amount of a hydrogen containing gas (which does not contain excessive hydrogen sulfide) charged through the line 44 in order to provide a mixture in the feed line 14 containing the desired amount of hydrogen and hydrogen sulfide.

As a still further alternative, all or a portion of the hydrogen sulfide may be removed from the gaseous products prior to recycling of the same. Thus, for example, the valve 36 may be closed and there may be opened a valve '5 in a line 48 leading to a hydrogen sulfide rcmoval zone such as a scrubber 52. Within the scrubber '52 the gaseous material is countercurrently contacted with a suitable scrubbing medium such as an aqueous solution of an alkali metal hydroxide such as sodium hydroxide, and the like, fresh scrubbing solution being charged to the scrubber 52 through a charge line 54 and spent scrubbing solution being Withdrawn through a discharge line 56. The scrubbed gaseous material passes from the scrubber 52 to a line '58 leading to the feed line 14. At the same time, additional hydrogen-containing sesis charged t th ed line 14 th h hy g n charge line 44- in order to provide for any deficiencies in hydrogen that may exist with respect to the recycled gaseous material.

As has been indicated, the reaction conditions to be employed in the desulfurization zone and therates of charge of the feed stock, hydrogen and hydrogen sulfide should be regulated in order to satisfy the hydrogen partial pressure requirements and themercaptan number control equation given above, whereby there is obtained a desulfurized product having improved Saybolt color characteristics and containing reduced amounts of gum and mercaptans.

The effect of operating conditions on desulfurization and the other above mentioned factors is shown by the following specific examples which are given inill-ustration and not as limitations on the scope of this invention.

EFFECT OF HYDROGEN SULFI'DE ON DESULFURIZATIO'N Example I Blends of catalytically and thermally cracked naphthas (including at times a small amount of thermal polymer naphtha) having a boiling range of 275 to 430 F. were desulfurized over a cobalt molybdate catalyst supported on a silica free alumina base in the presence of hydrogen in a series of runs under a variety of operations including the temperatures of 550 to 700 F., 4 to 16 v./v./hr., 250 to 1500 s. c. f. H /bbl. of oil, and 50 to 200 p. 's. i. g. and with up to about 10 mol percent H 8 in the total entering reactants. From these data it was determined that the degree of desulfurization obtained at otherwise constant operation condition is improved by the addition of extraneous H 3 as shown by the following table.

TABLE I [Percent desulfurization at 600 F., 8 v./v./hr., 1000 s. t. H2/bbl. and 200 p. s. i. g.]

Percent Reduction in Sulfur Content of Cracked Naphtha M01 Percent H28 in Entering Reactants Considered in another manner, the percent of desulfurization may be regulated by control of the H 5 level as shown below for the The effect of added hydrogen sulfide on the degree of desulfurization obtained is graphically set forth in Fig. 2, From Fig. 2 it will be noted that for otherwise constant operating conditions the percent desulfurization increases as the added hydrogen sulfide content increases.

SAYBOLT COLOR CHARACTERISTICS As has been indicated, the Saybolt color characteristics of desulfurized naphthas are improved when the desulfurization reaction is conducted in'the presence of hydrogen Sulfide. This is-shown by the following examples.

Example II Portions of blends of 275 to 430 F. boiling range cracked naphthas were desulfurized by contact with a TABLE III.MOLYBDENUM OXIDE CATALYST Mol Percent H28 in Reactants Entering Product Saybolt Color Minus Feed Saybolt Color Temp, F.

coo

TABLE IV.-COBALT MOLYBDATE CATALYST Mol Percent H28 in Reac- Product Saybolt Color Minus Feed Saybolt Color Temp, F.

Shades The results are graphically set forth in Figs. 3 and 4, respectively, of the drawings. From Fig. 3 it is seen that with a molybdenum oxide catalyst the improvement in Saybolt color characteristics progressively increases as the percent of hydrogen sulfide is increased to about 4 mol percent and that thereafter there is a slight tendency for a decline in the improvement obtainable.

With respect to Fig. 4 it is to be noted that with a cobalt molybdate catalyst there is a minimized improvement in Saybolt color characteristics when less than about 0.5 mol percent of hydrogen sulfide is employed but that with larger amounts of hydrogen sulfide the degree of Saybolt color characteristics improvement progressively increases.

GUM CONTENT As has been indicated, gum content is reduced in accordance with the present invention by conducting the desulfurization reaction in the presence .of hydrogen while maintaining a hydrogen partial pressure within the range of about 50 to p. s. i. a., as shown by the following examples- Example 111 With a molybdena catalyst, a plurality of runs were made at operating conditions of 500 to 700 F., 2 to 12 liquid hourly space velocities, 50 to 250 p. s. i. g. total pressures, 250 to 2000 s. c. f. H /bbl. oil and with blends of nominal 275 to 430 F. naphthas from catalytic and thermal cracking operations (in some cases including small amounts of naphthas produced by the thermal polymerization of olefins) the naphthas contained about 13 to 33 mg. of gum/1 ml. (General Motors Gum.) In these trials it wasfound that the gum contents of the treated naphthas were essentially determined by the partial pressure of the hydrogen in the reactor as shown by the datain the following table.

TABLE V.-MOLYBDENUM OXIDE CATALYST Average General Partial Pressure of Hydrogen in Motors Gum Reactor, p. s. 1. a. Content f Product, rug/100 ml.

With a cobalt molybdate catalyst similar beneficial effects were obtained by variations in hydrogen partial pressure but with this catalyst variations in temperature were also significant and temperatures of 600 F. and higher were found to be the most effective for reducing the gum content at constant hydrogen partial pressure.

substantially satisfy the mercaptan number control equation:

Product mercaptan number (M)=17.8+0.43

(v./v./hr.)+1.3 (percent H S)O.031 (T,)

This is shown by the following examples.

Example IV of about 1000 cubic feet of hydrogen per barrel of feed stock. The desulfurized product was analyzed for mercaptan number, Saybolt color and gum content. The amount of hydrogen sulfide added and the results obtained are set forth in Table VII. The calculated mercaptan number of the product was also derived from the mercaptan number control equation and is set forth in the table.

TABLE VIL-RESULTS OBTAINED BY DESULFURIZATION OF NAPHTHA FEED STOCK OVER COBALT LIOLYBDATE AT 600 F.; 8 V./V./HR.; 200 P. S. I. G. AND 1,000 CU. FT. 0F HgIBBL. OF FEED STOCK Added Hrs Mercaptrm No. Saybolt Color Shades Gum (mg/100 ml) Hydrogen Run (Moi Per- Partial No. cent of Pressure Total Feed Product Product Feed Product Improve- Feed Product (p. s. i. a.) Feed) (Found) (Cole) 1 ment 1 From the equation: M=17.8+0.43(v.lv./hr.)+1.3(Percent Has) -0.03(Tr).

In this instance the naphtha feed stock contained about 13 mg. of gum/100 ml. (General Motors). The etfeets of variations in partial pressure of hydrogen over the temperature range of 550 to 650 F. are given by the following data.

TABLE VI.-COBALT MOLYBDATE CATALYST General Motors Gum Content, mg./ 100 rnl.

Partial Pressure of Hydrogen in Reactor, p. s. i. a.

I MERCAPTAN CONTENT The postulated tendency towards the formation of tertiary mercaptans'during the desulfurization reaction ,is largely inhibited in accordance with the present invention by selecting reaction conditions sufficient to at least From Table VII it is to be noted that for the particular reaction conditions involved the mercaptan number of the product (both found and calculated) increased as the amount of hydrogen sulfide was increased. This series of runs shows, for example, that if it is desired to obtain a desulfurized product having a mercaptan number of less than about 5 with the reaction conditions employed it is necessary that not more than about 1.2 mols of H 8 be added.

In connection with Table VII it is also to be noted that in each instance the Saybolt color of the product was substantially improved with respect to the Saybolt color of the feed material and that there was also a significant reduction in gum content. 1

As another alternative, reaction conditions can be changed in order, for example, to permit the utilization of larger amounts of hydrogen sulfide without increasing the mercaptan number of the product as is shown by the following example.

Example V The naphtha blend of Example IV was desulfurized over a cobalt molybdate catalyst in the presence of hydrogen and various amounts ofadded hydrogen sulfide under the reaction conditions of Example IV with but one exception, namely, the use of a reaction temperature of about 650 F. The amount of hydrogen sulfide added, the hydrogen partial pressure within the reaction zone and the mercaptan number, Saybolt color and gum content of the products are set forth in Table TABLE VIIL-RESULTS OBTAINED BY DESU'LFU'RIZA'IION OF NAPHTHA FEEDSTOGK OVER COBALT IVIOLYBDATE AT 650 F.; 8 V. Hz/BBL. OF FEED STOCK /V./HR.;200 P. S. I. G. AND 1,000 CU'.FT..OF

Added H28 Mercaptan No. Saybolt Color Shades Gum (rug./100 ml) Hydrogen Run (M01 Per- Partial No. cent of Pressure Total Feed Product Product Feed Product lmprove- Feed Product 1(p. s. i. a.) Feed) (Found) (Gale) 1 ment 1 From the equation: M=17.8+0.43(v./v./hr.)+1,3(Percent H2s)0-03(T1).

From Table VIII it is to be noted that, under the reaction conditions employed there was .a significant eaptan number, Saybolt', color and gum content. The results are set forth i able TABLE IX.RESULTS OBTAINED BY DESULFURIZATION OFNAPHTHA FEED STOCK OVER MOLYBDENUM OXIDE AT'650" F2; 4 V.'/V./HR.;'200 P. S. I". G. :AND 1000 GU. FT. OF H2/BBL. OF FEED STOCK Added HQS Mercaptan No. Saybolt Color Shades Gum (mg;/100 ml) Hydrogen Run (Mol Per- Partial No. cent of Pressure Total Feed Product Product Feed Product Improve- Feed Product (p. s. i. a.)

Feed) (Found) (Cale) ment 8- 1. 07 0. 9 1. 9 2. 5 -11 +14 +2 5 13.- 4 2.2 Y 119 9 3.01 0.9 4.7 3.9 -11 +15 +26 13.4 4L0 119 10---. 3. 43 0.9 5. 1 6.0 11 +13 v +24 13.4 4.0 119 1 From the equation: M=17.8+0.43(v./v./hr.)+1.3(Bercent HzS) -0.03( Tr).

improvement in Saybolt color and a significant reduction of gum content.

It is further to be noted'from this example that in run number 5 wherein 1.2 mol percent of hydrogen sulfide was added, a product was obtained having a mercaptan number of about 2 (calculated mercaptan number 3). When this run is compared with run number 3 of Table VII, it is seen that a substantial reduction in product mercaptan number was obtained for the same feed stock and for the same amount of added hydrogen sulfide through the use of an increased temperature.

Similar results are obtainable with other desulfurization catalysts as is shown by the following example.

Example VI Example VII The hydrogen charge rate does not materially affect product mercaptan number as is shown by the results obtained through the desulfurization of a blend of catalytic and thermal naphthas having a feed mercaptan number of about 0.6 over a cobalt molybdate catalyst. The reaction conditions employed and the results obtained are set forth in Table X.

TABLE X.RESULTS OBTAINED BY DESULFURIZATION OF NAPHTHA FEED STOCK OVER COBALT MOLYBDATE 1 From the equation: M=17.8+0.43 (v./v./hr.)+1.3 (Percent H2S)0.03 (Tr).

oxide catalyst under reaction conditions including a temperature of about 650 F., a pressure of about 200 p. s. i. g., a space velocity of about 4 v./v./hr. and a hydrogen charge rate of about 1000 cubic feet .of hy- From Table X it will be noted that substantially the same reaction temperature, space velocity and pressure were employed in runs 11 and 12. In run 11 about 1.4 mol percent of hydrogen sulfide was added and a hydrogen charge rate of about 2,000 cubic feet per barrel of feed stock was employed. In run number 12 about 3 mol percent of hydrogen sulfide was added and a hydrogen charge rate of about 1,000 cubic feet of hydrogen per barrel of feed stock was employed. It will be noted that the mercaptan numbers of the products as found correlated well with the calculated mercaptan numbers and that the product mercaptan number (found and calculated) was, again, significantly affected by the amount of added hydrogen sulfide.

Having thus described our inventionwhat is claimed is:

1. A process which comprises the steps of desulfurizing a petroleum hydrocarbon boiling in the naphtha range in contact with a desulfurization catalyst in the presence: of about 250 to about 2,000 cubic feet of hydrogen per barrel of feed stock and about 1.0 to about 10 mol percent of added hydrogen sulfide (H 5), based on the total amount of feed material, under reaction conditions including a temperature within the rangeof about 500 to about 750 F. (T,),a space velocity in the range of about 1 to about 16 volumes of feed per volume of catalyst per hour (v./v./hr.), a reactor pressure within the range of about 50 to about 300 pounds per square inch gauge and a hydrogen partial pressure within the range of about 50 to about 150 pounds per square inch d ing a petroleum hydrocarbon naphtha boiling in the range of about 275 F. to about 430 F. in contact with a desulfurization catalyst in the presence of about 250 to about 2,000 cubic feet of hydrogen per barrel of feed stock and about 1.0 to about 10 mol percent of added hydrogen sulfide (H 8), based on the total amount of feed material, under reaction conditions including a temperature Within the range of about 500 to about 750 F. (T,), a space velocity in the range of about 1 to about 16 volumes of feed per volume of catalyst per hour (v./v./hr.), a reactor pressure within the range of about 50 to about 300 pounds per square inch gauge and a hydrogen partial pressure within the range of about 50 to about 150 pounds per square inch absolute, said reabsolute, said reaction conditions at least substantially satisfying the equation 1.3 (percent H S)0.03 (T,.)

wherein M has a value of about 0.1 to about 5, and re-" covering a desulfurized product.

2. A process as in claim 1 wherein the catalyst is a 7 4 action conditions at least substantially satisfying the equation Product mercaptan number (M) =17.8+

0.43 (v./v./hr.)+1.3 (percent H S)0.03 (T wherein M has a value of about 0.1 to 5, and recovering a desulfurized product,and fractionating said thus recovered product to obtain a product fraction boiling within the range of 275 to 430 F.

References Cited in the file of this patent UNITED STATES PATENTS De Rosset July 16, 1957 

1. A PROCESS WHICH COMPRISES THE STEPS OF DESULFURIZING A PETROLEUM HYDROCARBON BOILING IN THE NAPHTHA RANGE IN CONTACT WITH A DESULFURIZATION CATALYST IN THE PRESENCE OF ABOUT 250 TO ABOUT 2,000 CUBIC FEET OF HYDROGEN PER BARREL OF FEED STOCK AND ABOUT 1.0 TO ABOUT 10 MOL PERCENT OF ADDED HYDROGEN SULFIDE (5H2S), BASED ON THE TOTAL AMOUNT OF FEED MATERIAL, UNDER REACTION CONDITIONS INCLUDING A TEMPERATURE WITHIN THE RANG E OF ABOUT 500* TO ABOUT 750*F. (TR), A SPACE VELOCITY IN THE RANGE OF ABOUT 1 TO ABOUT 16 VOLUMES OF FEED PER VOLUME OF CATALYST PER HOUR (V./V./HR.), A REACTOR PRESSURE WITHIN THE RANGE OF ABOUT 50 TO ABOUT 300 POUNDS PER SQUARE INCH GAUGE AND A HYDROGEN PARTIAL PRESSURE WITHIN THE RANGE OF ABOUT 50 TO ABOUT 150 POUNDS PER SQUARE INCH ABSOLUTE, SAID REACTION CONDITIONS AT LEAST SUBSTANTIALLY SATISFYING THE EQUATION 